This application claims the priority of German Patent Document 100 15 576.6, filed in Germany, Mar. 29, 2000, the disclosure of which is expressly incorporated by reference herein.
The invention concerns a valve arrangement in a feed line to deliver fuel from a tank to an internal combustion engine. The valve arrangement consists of a valve housing with an inlet and outlet channel, and a valve with a movable valve head to seal the outlet channel from the inlet channel, whereby a feed pump is assigned to the feed line, and the valve head is in closed position when there is no feed pressure from the feed pump.
The tank system of a vehicle to supply the drive with liquid fuel consists of at least one tank that can be filled with fuel. The vehicle can be a motor vehicle (such as an automobile), watercraft, or an aircraft (such as an airplane or rotary-wing aircraft). The drive is provided by a combustion engine. The combustion engine can be an internal combustion engine or a propulsion unit. Both are supplied with liquid fuel (gas, kerosene). The fuel is conveyed by a feed pump from the tank in a feed line to the drive. There is a valve arrangement in the feed line between the feed pump and the combustion engine. When the combustion engine is not running, the valve arrangement closes the feed line, and prevents or delays the fuel level in the feed line from dropping quickly. This prior-art valve arrangement is designed as a check valve.
At locations with a hot climate, the fuel in the tank system expands when the drive stops after an operating phase. It is problematic when the fuel expands in the feed line that connects the tank with the combustion engine. The feed line is usually in the tank along with a feed pump, and it is connected to an injection module of the combustion engine. After the combustion engine stops, the pressure of the fuel extends the entire length of the feed line. When the outside temperature is high, the fuel is additionally heated, which causes impermissibly high pressure to be exerted on the feed line and the connected assemblies. There is therefore a danger of fuel leakage directly adjacent to the combustion engine that can be triggered by increased pressure in the feed line. The fuel conventionally leaks at the connecting sites of the feed line. There is danger of fire when fuel leaks from the feed line.
The problem of the invention is to eliminate the danger of leakage from the feed line for combustion engines that burn liquid fuel. This also involves not requiring additional space to solve the problem.
The problem is solved according to certain preferred embodiments of the invention by placing within the valve another essentially coaxial valve that is in open position against the feed direction when the pressure at the outlet channel side is greater than the feed pressure.
In certain preferred embodiments of the valve of the invention, there is an axial through-hole running through the valve head and its valve stem that represents a guide, and the through-hole has a valve seat at the mouth facing the outlet channel.
The other valve with its valve stem can be guided within this guide. Between the valve stem of the other valve and the wall of the through-hole, there is a gap that extends the length of the through-hole. One end of the other valve stem guided in the valve stem is designed as a valve cone that can be positioned to seal the valve seat of the through-hole by a resistance means. The valve cone can be opened against the feed direction. This produces a constructively simple and economical design.
In certain preferred embodiments of the valve of the invention, it is provided that the valve stem can be moved against a force of the resistance means in the guide.
In certain preferred embodiments of the valve of the invention, the resistance means is a spring, e.g. a spiral spring.
In certain preferred embodiments of the valve of the invention, it is suggested that the resistance means for the valve cone has a settable threshold for switching the other valve between open and closed position. When the threshold for e.g. a specific spring force of the resistance means is exceeded, the valve switches from the closed position to the open position. The threshold for the spring force is equivalent to a specific pressure in the feed line that is greater than the feed pressure.
Certain preferred embodiments of the invention advantageously enable a valve cone of a valve acting against the original feed direction to be placed in the valve head of a check valve. Advantageously, no additional installation space is required. Two coaxial valves are integrated in a common housing to form a single valve arrangement.
The valve arrangement according to the invention can work as a check valve when the combustion engine is running, and it can independently function as a pressure relief valve when the engine is not running. The valve according to the invention can be economically integrated into existing fuel systems without much installation effort.